Early Childhood

Preschool Class Size—Within Reason—Doesn’t Matter, Study Finds

By Christina A. Samuels — August 04, 2017 2 min read
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Regulations that hold preschool class sizes at or below 20 and that require one teacher for every 10 children, are largely adequate for most children, according to a recent study that analyzed nearly six decades’ worth of early-childhood research.

To see a positive difference in cognitive or achievement outcomes, classes had to get very small, according to the findings, which will be published in the September print edition of Educational Evaluation and Policy Analysis. Only child-to-teacher ratios of 7.5 to 1 or lower, or class sizes of 15 children or fewer, were linked to benefits for children. And those benefits, while statistically significant, were not large.

For social-emotional outcomes, the study suggested that very small classes might have a positive effect, but they didn’t see any impact from low child-teacher ratios. Because the sample size was small, the researchers were less confident in that result.

The research separated out the effects of class size and child-teacher ratios, because, while these are related, they may produce distinct impacts on children. A classroom with fewer children is potentially less chaotic, easier for teachers to manage, and more easily allows children to engage in appropriate activities and cooperative play. A low child-to-teacher ratio allows teachers more time to individually interact with every child.

Overall, the study suggests that it might not be cost effective to spend limited funds to reduce class sizes or to decrease child-teacher ratios, said lead author Jocelyn Bonnes Bowne, currently a senior research specialist with the Massachusetts Department of Education. She is managing the state’s preschool expansion grant.

But there are a couple of important caveats, Bowne noted. One is that the study didn’t focus on children who might have high needs. “Committing the resources to very small classrooms and rations might be important to do” for children from very adverse backgrounds, she said.

The other caveat is that the range of class sizes studied was not extreme—there were no 50-child classrooms, for example, or teachers forced to manage dozens of children on their own. In the sample of studies, child-teacher ratios ranged from 5 to 1 to 15 to 1, with an average of around 9 to 1. Class sizes ranged from 11 to 25 children, with an average class size of about 17.

“Largely, if you’re within what is typical, we do think reducing class sizes by small amounts is not going to gain you much in terms of results,” Bowne said.

The researchers did look at some well-known programs with very low class sizes and child-teacher ratios. Perry Preschool, a 60s-era intervention, found positive benefits from participants well into their adulthood. But Perry, a demonstration program, was an intensive program that blended preschool with a home visiting component. Head Start was also a program studied that tended to have low class sizes and teacher ratios.

But it’s not likely that the benefits seen in those programs would be seen at scale, Bowne said: for one thing, it’s difficult to find a large enough pool of qualified teachers to staff such a program if it was expanded to thousands of children.


A version of this news article first appeared in the Early Years blog.